Molecular mechanisms of tributyltin-induced cellular damage : possible involvement of the immediate early genes

在CCRF-CEM人T细胞株中，研究了三丁基氯化锡（TBT）和其他有机锡化合物对丝裂原活化蛋白激酶（MAPKs）的影响。细胞外信号调节蛋白激酶（ERK）、c-Jun n -末端激酶（JNK）和p38 MAPK磷酸化形式的水平呈剂量依赖性增加。在TBT暴露后15分钟和4小时观察到磷酸化。另一方面，ERK、JNK和p38 MAPK的总蛋白水平未见明显变化。MAPKs磷酸化电位为TBT >二氯化二丁基锡>三氯化一丁基锡。与其他三有机锡化合物（如三甲基氯化锡、三苯基氯化锡和三乙基溴化锡）相比，TBT暴露诱导的MAPKs磷酸化最为显著。细胞内Ca^<2+>与BAPTA/AM的螯合抑制tbt诱导的MAPKs磷酸化和随后的细胞凋亡。这些结果表明，三丁基锡是ERK， JNK和p38 MAPK途径的有效激活剂，细胞内Ca^<2+>在MAPKs磷酸化中起重要作用。MAPKs的磷酸化和随后的直接早期基因的表达可能是tbt诱导的细胞损伤的原因。暴露于镉或无机汞也会诱导CCRF-CEM细胞中MAPKs的磷酸化。发现ERK参与镉诱导的T细胞系细胞凋亡。LL-Z1640-2是一种大环非aketide，是CCRF-CEM细胞中金属诱导的MAPKs激活的有效抑制剂。已知TBT和其他金属可诱导c-fos基因在各种细胞类型中的表达。在暴露于TBT和其他金属后，缺乏c-fos的成纤维细胞比野生型细胞受到更严重的影响，这表明至少在成纤维细胞中，c-fos可能对金属的细胞毒性作用起保护作用。

Effects of tributyltin chloride (TBT) and other organotin compounds on mitogen-activated protein kinases (MAPKs) were examined in CCRF-CEM human T cell line. The levels of phosphorylated form of extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 MAPK increased in a dose-dependent manner. The phosphorylation was observed after 15 min and lasted for 4 h following TBT exposure. On the other hand, no clear changes were found in the total protein levels of ERK, JNK and p38 MAPK.The potential of MAPKs phosphorylation was TBT > dibutyltin dichloride > monobutyltin trichloride. When compared to other triorganotin compounds such as trimethyltin chloride, triphenyltin chloride and triethyltin bromide, TBT exposure induced the most marked phosphorylation of MAPKs. Chelation of intracellular Ca^<2+> with BAPTA/AM suppressed TBT-induced MAPKs phosphorylation and subsequent apoptosis. These results showed that tributyltin is a potent activator of ERK, JNK and p38 MAPK pathways, and intracellular Ca^<2+> plays an important role for MAPKs phosphorylation. Phosphorylation of MAPKs and subsequent expression of the immediate early genes may be responsible for TBT-induced cellular damage. The exposure to cadmium or inorganic mercury also induced the phosphorylation of MAPKs in CCRF-CEM cells. ERK was found to be involved in cadmium-induced apoptotic cell death in this T cell line. LL-Z1640-2, a macrocyclic nonaketide, was a potent inhibitor of metals-induced MAPKs activation in CCRF-CEM cells.TBT and other metals have been known to induce the expression of c-fos gene in the various cell types. The c-Fos-deficient fibroblasts were more severely affected than wild-type cells following the exposure to TBT and other metals, suggesting that c-fos may play a protective role against the cytotoxic effects of metals at least in fibroblasts.